1. Field of the Invention
The present invention relates to an image forming apparatus and, more particularly, to a damping structure for preventing noises caused by a vibration of a vibration generating source.
2. Description of the Related Art
Hitherto, an image forming apparatus such as printer, copying apparatus, or the like has a sheet feeding apparatus for feeding sheets one by one from a sheet enclosing portion in which a plurality of sheets have been enclosed. As such a sheet feeding apparatus, there is an apparatus of an air sheet feeding system in which a plurality of sheets are floated by blowing air to an edge portion of a bundle of sheets enclosed in the sheet enclosing portion and only one sheet is adsorbed to an adsorption conveying belt arranged in an upper position and is conveyed. Such a technique has been disclosed in Japanese Patent Application Laid-Open No. H07-196187.
Such a sheet feeding apparatus of the air sheet feeding system has: a motor as a driving source of the adsorption conveying belt which is driven when feeding the sheet; and an axial-flow fan for blasting. Since those motor and fan execute the rotating operation, a vibration will occur upon operation so that the vibration changes to a sound.
Even if the motor and the fan do not generate noises in the operation of itself, when the motor and the fan (hereinbelow, referred to as a motor or the like) are attached to an apparatus main body, the vibration of the motor or the like vibrates a frame such as an attached sheet metal of the apparatus main body. When the frame vibrates as mentioned above, the noises are generated, and a disturbance of an image also occurs by the vibration of the frame when the image is formed.
To solve such a problem due to the vibration, therefore, in the sheet feeding apparatus in the related art, a damping member made of an elastic member such as rubber is interposed between a vibration generating source as a vibrating source such as a motor and a holding member to which the vibration generating source is fixed. In the case of fixing the vibration generating source to the holding member with a screw, the damping member is sandwiched in a fastening portion.
In the fastening portion where the vibration generating source is fixed to the holding member, the damping member is sandwiched between the vibration generating source and the holding member. If the damping member is sandwiched in this manner, the damping member is compressed. When the damping member is compressed, hardness of the damping member (elastic member) rises and the damping member enters a state where the vibration is liable to be propagated, so that the propagation of the vibration in the fastening portion increases.
FIG. 8 is a diagram illustrating an example of the damping structure of the vibration generating source in the related art. As illustrated in FIG. 8, a vibration generating source 3 as a vibrating source for generating a vibration of a fan, a driving motor, or the like is fixed to a holding member 2 such as a frame. In this state, a damping member 81 such as rubber is sandwiched between the vibration generating source 3 and the holding member 2 by an attaching screw 4 and a fastening portion 82 provided for the holding member 2.
If the vibration generating source 3 is the fan, one of an air inlet and an air outlet is provided on the holding member side. If the air inlet is provided in this manner, in order to assure an air duct between the fan and the holding member 2, a sealing member 7 having elasticity is arranged between the vibration generating source 3 and the holding member 2 as illustrated in FIG. 8.
However, since the damping member 81 enters a compressed state since it is sandwiched, in a state where the vibration generating source 3 has been fixed, hardness of the damping member 81 rises and the vibration of the vibration generating source 3 is liable to be propagated. A vibration propagating path according to such a fixing method is constructed in order of the vibration generating source 3→the damping member 81→the holding member 2, and a distance of the vibration propagating path in this case is equal to “a”.
FIG. 9 is a diagram illustrating another example of a damping structure in the related art. According to this damping structure, after a damping member 83 was inserted into a through-hole 85 formed in the holding member 2, the vibration generating source 3 is brought into pressure contact with the holding member 2 through the sealing member 7 and fixed thereto by the attaching screw (bolt) 4 and a fastening portion (nut) 84 provided for the damping member 83. When the damping member 83 is brought into pressure contact with the vibration generating source 3 in this manner, the damping member 83 is elastically deformed and is brought into contact with both of the front and back surfaces of the holding member 2 and the inner wall surface of the through-hole 85. According to such a damping structure, the vibration generating source 3 is fixed so as to sandwich the damping member 83 between the vibration generating source 3 and the holding member 2 while being compressed. Therefore, a vibration propagating path is constructed in order of the vibration generating source 3→the damping member 83→the holding member 2. Thus, a distance of such a vibration propagating path is also equal to a and such a is substantially the same as the damping structure illustrated in FIG. 8.
In the image forming apparatus in which the vibration generating source has been fixed by the damping structure in the related art as mentioned above, if the suppression of the vibration propagation is insufficient, a countermeasure for thickening the damping member is taken, for example.
If the vibration generating source is the motor, since a member to be driven by the motor is generally provided for the holding member on the side opposite to the motor, a motor shaft for propagating a driving force of the motor is arranged so as to be extended to the left in FIGS. 8 and 9. Therefore, if the damping member is thickened, it is necessary to extend a length of motor shaft. However, if the length of motor shaft is extended, an influence of the eccentricity of the shaft is exerted on the motor by an extended amount of the motor shaft, so that an inconvenience is liable to occur in vibration propagating efficiency.
If the vibration generating source is the fan, the sealing member is used in order to assure the air duct between the vibration generating source and the holding member. In this case, if the damping member is thickened, a distance between the fan and the holding member increases by a thick amount of the damping member in association with it. It is necessary to thickening (enlarging) the sealing member. When the distance between the fan and the holding member further increases, a sealing area is widened, and it becomes difficult to assure a sealing degree. Thus, a possibility of an air intake/exhaust loss increases and intake or exhaust efficiency deteriorates.